How to build a simple but cool IR (Infra Red) receiver.

This circuitry allows you to control your computer with a simple remote, like
the one you already use for your TV-set. It's very useful when you want to control
a DVD or an mp3 player without having to stay at the keyboard; I use it for
VDR and now my pc
is a full featured set top box connected to the television, capable to digitally
record and replay satellite television, DVDs and every kind of digital content
(mp3, divx).
You can use LIRC for Linux
or WinLIRC, the windows port.

I wrote this guide after having built few receivers; I've found
a quick and easy way to hold all the circuitry inside the serial connector
and I want to keep memory of this:

Let's see the 'ingredients' of this IR recipe:

the circuit is rather simple, allowing to be built directly inside the 9-pin
serial connector.